Nowadays, various kinds of digital projector are commercially available, such as liquid crystal display (LCD) projectors, digital light processing (DLP) projectors, and liquid crystal on silicon (LCOS) projectors. The LCD projector operates in a transmissive way, with the light beam directly passing through the imaging device and lens. The DLP projector and the LCOS projector operate in a reflective way, with the light beam of high brightness being reflected by the imaging device before passing through the lens.
The LCOS display is a key technique of the reflective LC projectors and rear-projection TVs. The most favorable advantages of the LCOS display panel are low production cost and high resolution. In comparison to a typical LCD panel, the upper and lower substrates of the LCD panel are glass while the upper substrate of the LCOS panel is glass and the lower substrate is mainly a semiconductor material, silicon. Therefore, manufacture of the LCOS display panel involves techniques of the typical LCD panel and complementary metal-oxide semiconductor (CMOS) processes.
Reference is made to FIG. 1, which depicts a cross-sectional structure of the LCOS display panel in the prior art. Typically, the structure of the LCOS display panel in the prior art includes a parallel pair of a semiconductor substrate 101 and a transparent substrate 121, wherein an active array of transistor circuitry (not shown) is fabricated by the CMOS process and disposed in the semiconductor substrate 101. Pixel electrodes 103 and a passivation layer 111 are disposed on the semiconductor substrate 101, in turn, wherein the pixel electrodes 103 are smooth mirrors with high reflectivity, and the passivation layer 111 prevents the pixel electrodes 103 from being damaged. At least one common electrode 123 is disposed on a surface of the transparent substrate 121 with respect to the pixel electrodes 103 of the semiconductor substrate 101, wherein the common electrode 123 is a transparent conductive layer. A liquid crystal layer 125 is formed between the transparent substrate 121 and the semiconductor substrate 101. Ideally, the transistor circuit generates only a vertical electric field 130 between each pixel electrode 103 and the common electrode 123, whereby an LC molecule 126 tilts to a desired angle.
However, the transistor circuit in practice also generates a lateral electric field 140 between the neighboring pixel electrodes 103. The LC molecules 126 located between the neighboring pixel electrodes 103 are affected by both electric fields 130 and 140, and do not tilt to the desired angle. Such a fringe effect causes light leakage between the neighboring pixel electrodes 103 and seriously reduces the contrast of the image projected on the screen.